Get Ahead of the Fund Managers

Some traders see a seasonal opportunity: Buy calls that will pay off as managers chase stocks higher.

Aggressive traders are positioning themselves in the options market to profit from what they see as a seasonal trading opportunity -- the expectation that mutual-fund managers are about to buy a ton of stocks.

Traders are buying call options on the SPDR S&P 500 ETF Trust (ticker: SPY) on the assumption that mutual-fund managers will be forced to chase the market higher on Friday, the first day of a new month. Most managers lagged...